Information search and retrieval systems have provided tools for finding information. Such tools provide the capability to search for data listed in directories by name, perform free-text searching, or to search using Boolean expressions in text form. These systems, however, did not account for the fact that a user performing a search may need to use more than one style or approach to effectively find the information being sought. For example, a free-text search such as those found commonly on traditional search engines may be helpful in some cases, but in other cases may not allow for the serendipitous discovery afforded by browsing through data displayed in an organized list.
In addition, many of the tools provided by the information search and retrieval systems suffered from drawbacks such as poor ease of use, lack of structure and controlled vocabulary, and difficulty in combining information from multiple facets. Furthermore, many of the tools allowed for searching of information in either a coarse-grained level or a fine-grained level of detail, but not both.